Both pronunciations are in use. As we explained when GIF was selected as Oxford Dictionaries USA Word of the Year 2012, ‘GIF may be pronounced with either a soft g (as in giant) or a hard g (as in graphic). The programmers who developed the format preferred a pronunciation with a soft g (in homage to the commercial tagline of the peanut butter brand Jif, they supposedly quipped “choosy developers choose GIF”). However, the pronunciation with a hard g is now very widespread and readily understood.’ A coiner effectively loses control of a word once it’s out there; for instance, the coiner of quark in the physics sense had intended it to rhyme with cork, but general usage has resulted in it rhyming with mark. Whichever pronunciation you use for GIF, it helps if it’s the same for both the noun and the verb.”

If anyone gets to have the final say on how a word is pronounced, it’s this guy.

As has been pointed out on social media, the “g” in gif stands for “graphics,” not “japhics.”